Filament and reflector support for an elongated tube



Dec. 8, 1964 R. H. HOLCOMB 3,160,777

FILAMENT AND REFLECTOR SUPPORT FOR AN ELONGATED TUBE Filed Oct. 22, 1962ITWVTTTOVI Richard H. HoLcomb b9 g/i/fi/i His A t lr neg United StatesPatent p This invention relates generally to electric incandescentlamps, and more particularly to tubular doubleended lamps comprising anelongated tubular envelope having an incandescible filament extendingaxially thereof.

There is available on the market an infrared or heat lamp of the typedisclosed and claimed in US. Patent 2,864,025, to Foote et al.,comprising a slender tubular quartz envelope having an elongated coiledfilament extending therethrough and connected at its ends to lead-inconductors sealed through pinch seals at the end of the envelope, thefilament being supported in the envelope axis by support members ofsheet metal or of Wire engaging the filament and, in turn, engageablewith the inner wall of the envelope. In some applications, such lampsare used in conjunction with elongated reflectors where it is desired toconcentrate the energy radiated from the lamp in a given direction. Itwould be desirable to incorporate the reflector as an integral elementof the lamp in some applications where an external reflector is notfeasible. Accordingly, attempts have been made to place a reflectingsurface on the outside of the lamp envelope. Since the envelope becomesheated to a high temperature, approximately 500 C. for example, duringoperation of the lamp, the reflector material must be exceptionallyresistant to oxidation. However, the metals that have good reflectingproperties and are suitable for use in an ambient of air, such as gold,platinum or rhodium, adhere poorly to the quartz envelope or are easilyabraded. On the other hand, a metallic reflector cannot be incorporatedinside the conventional lamp structure because it would short circuitthe filament through the support member.

Accordingly, it is an object of the invention to provide a novelstructure which permits incorporating the reflector within the lamp. Itis a further object to provide a lamp structure wherein the internalreflector and the filament supporting members are effectively maintainedout of electrical contact with one another.

To that end, and in accordance with a preferred aspect of the invention,the lamp envelope is provided with a pair of longitudinally extending,circumferentially spaced ridges or ribs which divide the envelope intoopposed sides, and the reflector is located at one of said sides betweenthe ribs whereas the filament supports are located at the other side,the ribs thereby serving to maintain the filament supports and thereflector out of electrical contact with each other.

Further features and advantages of the invention will appear from thefollowing detailed description and from the drawing wherein:

FIG. 1 is a side view, partly in section, of a lamp embodying theinvention;

FIG. 2 is a transverse section through the lamp;

FIG. 3 is a fragmentary longitudinal section through a portion of thefilament and one of the support members;

FIG. 4 is a fragmentary perspective view of one end of a reflectorprovided with a supporting tab;

FIG. 5 is a front elevation of a support disc;

FIG. 6 is a transverse section through a lamp having a modified form offilament support member; and

FIG. 7 is a fragmentary side view of a portion of the filament andsupport member of FIG. 6.

Referring to FIG. 1 of the drawing, the lamp illustrated by way ofexample is of the infrared lamp type 3,160,777, Patented Dec. 8, 1 964diameter, usually about inch, having each end closed by a. pinch seal 2through which extends a lead-in conductor 3 having a. thin foliatedintermediate portionv 4 1 hermetically sealed in the seal 2. Anincandescible helically coiled, tungsten wirefilament 5 extendslongitudinally of the envelope 1 and is connected at its end to theinner ends of the respective lead wires 3.

In accordance with the invention, the envelope is provided with a pairof circumferentially spaced, longitudinally extending ridges or rib 6(FIGS. 1 and 2) on its inner surface. The ribs are here showndiametrically opposed and dividing the interior of the circular tubecross section into opposed halves. In one half of the envelope there isdisposed a reflector 7. Although the reflector 7 may in some cases beconstituted of a metallic coating vapor deposited on the inner surfaceof the envelope, it is preferably composed of a sheet metal membersupported by and between the ribs 6. In the illustrated example, thereflector 7 consists of a thin arcuate sheet of copper, about .005 inchthick for example. In order to provide adequate support for thereflector, it is in this case provided at each end with an overlyingarcuate tab 8 (FIG. 4) of suitable resilient sheet metal such asmolybdenum. The tab 8 may be spot welded at its center to the reflector7 and is originally formed to a larger radius than the reflector 7 sothat it springs outagainst the ribs 6 and securely holds the reflectorin place. It'will be evident that the reflector 7 may be made in itsentirety of a suitable self-supporting resilient metal such asmolybdenium and clamped in place between the ribs 6 and the envelopewall. The reflector may also be made of any desired cross sectionalshape such as parabolic, elliptical, circular, etc.

Although the tabs 8 hold the reflector 7 in place quite securely,further provision may be made to prevent 1ongitudinal displacement ofthe reflector by providing suit able stops, for example in the form ofinwardly protruding dimples or indentations in the Wall of the envelope1 as indicated at 20.

As illustrated in FIGS. 2, 3 and 5, the filament 5 is supported in theaxis of the envelope 1 by a series of spaced wafers or discs 9 which arepreferably a modified form of the conventional disc structure disclosedand claimed in US. Patent 2,813,993 to Fridrich. As shown in FIG. 5, theconventional support comprises a circular disc including the portion 10shown in broken lines and having a sector shaped radial slot extendinginwardly from the periphery of the disc to provide for inserting thedisc in place transversely of the filament 5, i.e., a turn of thefilament coil 5 extends through said slot 11. At the center of the disc,the slot 11 terminates in a central opening having at its margin acollar portion 13 located within the coil 5 and comprised of a pluralityof tongues or tabs engaging and gripping the inner side of an adjacentturn of the coil 5 to assist in holding the disc in place betweenadjacent coil turns. For purposes of the present invention, a generallysector shaped portion of the disc is formed by removing the portionshown in broken lines by cutting along a radius 14 aligned with thecenter of the radial slot 11, and along the arc 15 joining the radius 14and the slot 11. The radius 14 and the remaining full length edge of theslot 11 thus serve to confine the wafer or disc 9 between the ribs 6(FIG. 2) at the side of the envelope 1 opposite the side occupied by thereflector 7 and out of electrical contact with said reflector. Thefilament 5 is thereby held at the hub portion of the sector shaped wafer9 which is in turn supported from the portion of the envelope wallbetween the ribs 2 or by the ribs themselves, depending upon theorientation of the envelope.

r Y K 1:3

The filament support 16 shown in FIGS. 6 and 7 is formed from arefractory wire such as tungsten. The

Wire is formed with several helical turns 17 at its center and is of adiameter. to snugly-norv forcibly fit betweenthe turns of; the filamentcoil 5. From the center turn 17 there extend leg portions "IS Whichfitbehindtheribs 6 and which preferably terminatein bent. end portions ,19

, which arev engageable with the envelope wallsand assist.vv

in positioning the support. It will be-evidentthat, if desired, the.bent endsl9: may be continuedfto form a'clos'ed loop. The sheetlmetalreflector 7.' isnself.supporting and is locked behind the ribs 6 at theside'ofvthe envelope .op

posite. the side occupied by the. supports. 16... It will be noted thatin this case' thereflector 7.[has a curvature differing from that of theinner envelope Wall.

fWhatLclaim as new and desire to secure by Letters Patent of the" UnitedSt-ate'sis:

interior of said envelope, an elongated metallic reflector at one sideof said envelope between said ribs, and metallic filament support meanssupporting said filament and confined between said ribs to be engageablewith and supported from the other sideof said envelope out of electricalcontact with said reflector.

l interior of said envelope, an elongated reflectorofsheet metalsupported at one side of said envelope by and betweensaid ribs, andmetallic-filament support means supporting saidfilament and confinedbetween said ribs =to be' engageable with and supported from the otherside of said envelope out ofelectrical contact withsaidre fiector.

lLAn-electric incandescent lamp comprising. an clon V .gated tubularenvelope, a-filamentjextending longitudinally of the-interior of saidenvelope,anelongat'ed metallic reflector within said envelope at oneside thereof, metallic filament support means supporting said filamentand engageable with the side of said envelope opposite that occupied bysaid reflector, and means maintaining said reflector and said filamentssupport means at. their respective sidesof the envelope, and outofelectrical contact with each other.

' 2. An electric incandescent lampcomprising an elongated tubularenvelope, having a pair of circumferentially spaced internal ribsextending longitudinally of the interior surface" thereof and dividingsaidnenvelope into opposedsides, a filament extending longitudinally ofthe 4. An. electric incandescent lamp comprising an elongatedtubularenvelope having a pair of circumferentially spaced internal ribsextending longitudinally of theinteriorJsurfacethereof and dividing saidenvelope intoop- 1. posed sides, a filament extending longitudinally oftheinterior. of said envelope, an elongated metallic vreflector at oneside of said envelope between said ribs, and: a

metallic filament supportmember comprising a generally sector shapedWafer. supporting said filamentadjacent its hub and. havingacircumferential extent confining said water betweensaid ribs to beengageable withand supported from theother side ofsaidenvelope out ofelectrical contact withsaid reflector.

No references cited.

1. AN ELECTRIC INCANDESCENT LAMP COMPRISING AN ELONGATED TUBULARENVELOPE, A FILAMENT EXTENDING LONGITUDINALLY OF THE INTERIOR OF SAIDENVELOPE, AN ELONGATED METALLIC REFLECTOR WITHIN SAID ENVELOPE AT ONESIDE THEREOF, METALLIC FILAMENT SUPPORT MEANS SUPPORTING SAID FILAMENTAND ENGAGEABLE WITH THE SIDE OF SAID ENVELOPE OPPOSITE THAT OCCUPIED BYSAID REFLECTOR, AND MEANS MAINTAINING SAID REFLECTOR AND SAID FILAMENTSSUPPORT MEANS AT THEIR RESPECTIVE SIDES OF THE ENVELOPE AND OUT OFELECTRICAL CONTACT WITH EACH OTHER.